---
layout: docs
page_title: Why use Agent or Proxy?
description: >-
  Use Vault tools like Agent and Proxy to simplify secret fetching and add Vault
  to your development environment with minimal client code updates.
---

# Why use Agent or Proxy?

A valid client token must accompany most requests to Vault. This
includes all API requests, as well as via the Vault CLI and other libraries.
Therefore, Vault clients must first authenticate with Vault to acquire a token.
Vault provides several authentication methods to assist in
delivering this initial token.

![Client authentication](/img/diagram-vault-agent.png)

If the client can securely acquire the token, all subsequent requests (e.g., request
database credentials, read key/value secrets) are processed based on the
trust established by a successful authentication.

This means that client application must invoke the Vault API to authenticate
with Vault and manage the acquired token, in addition to invoking the API to
request secrets from Vault. This implies code changes to client applications
along with additional testing and maintenance of the application.

The following code example implements Vault API to authenticate with Vault
through [AppRole auth method](/vault/docs/auth/approle#code-example), and then uses
the returned client token to read secrets at `kv-v2/data/creds`.

```go
package main

import (
    ...snip...
    vault "github.com/hashicorp/vault/api"
)

// Fetches a key-value secret (kv-v2) after authenticating via AppRole
func getSecretWithAppRole() (string, error) {
    config := vault.DefaultConfig()

    client := vault.NewClient(config)
    wrappingToken := ioutil.ReadFile("path/to/wrapping-token")
    unwrappedToken := client.Logical().Unwrap(strings.TrimSuffix(string(wrappingToken), "\n"))

    secretID := unwrappedToken.Data["secret_id"]
    roleID := os.Getenv("APPROLE_ROLE_ID")

    params := map[string]interface{}{
        "role_id":   roleID,
        "secret_id": secretID,
    }
    resp := client.Logical().Write("auth/approle/login", params)
    client.SetToken(resp.Auth.ClientToken)

    secret, err := client.Logical().Read("kv-v2/data/creds")
    if err != nil {
        return "", fmt.Errorf("unable to read secret: %w", err)
    }

    data := secret.Data["data"].(map[string]interface{})

    ...snip...
}
```

For some Vault deployments, making (and maintaining) these changes to
applications may not be a problem, and may actually be preferred. This may be
applied to scenarios where you have a small number of applications, or you want
to keep strict, customized control over how each application interacts with
Vault. However, in other situations where you have a large number of
applications, as in large enterprises, you may not have the resources or expertise
to update and maintain the Vault integration code for every application. When
third party applications are being deployed by the application, it is prohibited
to add the Vault integration code.

### Introduce Vault Agent and Vault Proxy to the workflow

[Vault Agent][vaultagent] and [Vault Proxy][vaultproxy] aim to remove this initial hurdle to adopt Vault by providing a
more scalable and simpler way for applications to integrate with Vault. Vault Agent can
obtain secrets and provide them to applications, and Vault Proxy can act as
a proxy between Vault and the application, optionally simplifying the authentication process
and caching requests.

As with most other CLI commands for the Vault binary, neither Vault Agent nor Vault Proxy
require a Vault Enterprise license, and are available in all Vault binaries and images. Note
however that some features, such as [static secret caching][static-secret-caching], are only
available when connected to a Vault Enterprise server.

| Capability                                                                               |    Vault Agent     | Vault Proxy |
|------------------------------------------------------------------------------------------|:------------------:|:-----------:|
| [Auto-Auth][autoauth] to authenticate with Vault                                         |         x          |      x      |
| Run as a [Windows Service][winsvc]                                                       |         x          |      x      |
| [Caching][caching] the newly created tokens and leases                                   |         x          |      x      |
| [Templating][template] to render user-supplied templates                                 |         x          |             |
| [Process Supervisor][exec] for injecting secrets as environment variables into a process |         x          |             |
| [API Proxy][apiproxy] to act as a proxy for Vault API                                    | Will be deprecated |      x      |
| [Static secret caching][static-secret-caching] for KV secrets                            |                    |      x      |

To learn more, refer to the [Vault Agent][vaultagent] or [Vault
Proxy][vaultproxy] documentation page.


[autoauth]: /vault/docs/agent-and-proxy/autoauth
[caching]: /vault/docs/agent-and-proxy/proxy/caching
[static-secret-caching]: /vault/docs/agent-and-proxy/proxy/caching/static-secret-caching
[apiproxy]: /vault/docs/agent-and-proxy/proxy/apiproxy
[template]: /vault/docs/agent-and-proxy/agent/template
[exec]: /vault/docs/agent-and-proxy/agent/process-supervisor
[template-config]: /vault/docs/agent-and-proxy/agent/template#template-configurations
[vaultagent]: /vault/docs/agent-and-proxy/agent
[vaultproxy]: /vault/docs/agent-and-proxy/proxy
[winsvc]: /vault/docs/agent-and-proxy/agent/winsvc
